1. Field of the Invention
The present invention relates to a modulator, and more particularly to a modulator that uses a detector to detect the voltage between a feedback device and a first transistor, so as to reduce any excessively high output voltage resulted from plugging/unplugging or suddenly starting a load device.
2. Description of Related Art
As mobile electronic technologies are increasingly advancing, electronic products such as note book, PDA, mobile phones and digital cameras are extensively used, and the functions of these products are increased. Therefore, more power consumption is required by a system, and thus many ways of reducing power consumption during an idle time or in a sleep mode is introduced. If an idle mode is switched to an operating mode, the system will need to start or turn on a feedback device. Attentions should be paid to a sudden climb of an output voltage (VOUT) to prevent its load device from being damaged by an excessively high output voltage. Besides, it is necessary for an idle system to minimize the power consumption of a battery; therefore the way of designing an efficient power management system is an important subject to most designers and developers.
Referring to FIG. 1, related components will be illustrated below, but other components are well known by the persons skilled in the art and thus will not be described here. The description below is given as illustrations and is not intended to limit the present invention. In FIG. 1, the prior art modulator comprises a differential amplifier A connected to a PMOS transistor B; a source pole B1 of the PMOS transistor B provided for receiving power; a drain pole B2 of the PMOS transistor B provided for connecting a feedback device C; a voltage divider node D of the feedback device C connected to a load voltage input terminal A1 of the differential amplifier A; and an reference voltage input terminal A2 of the differential amplifier A for inputting a reference voltage.
When the system starts operating, output voltage (VOUT) is started from a ground potential. The ground potential will be pulled-up rapidly due to the effect of the feedback circuit to increase the impetus of the PMOS transistor B. Therefore, the feedback device C will instantly climb to the power supply voltage (VCCAH) and produce an excessively high output voltage, and such phenomenon will cause damages to an output load device (such as a flash memory).